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From:   "Rafael J. Wysocki" <rjw@rjwysocki.net>
To:     Linux PM <linux-pm@vger.kernel.org>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        "elaine.zhang" <zhangqing@rock-chips.com>
Subject: [PATCH v2] PM: runtime: Update device status before letting suppliers suspend
Date:   Thu, 25 Feb 2021 19:23:27 +0100
Message-ID: <2024466.aZ6alR0V7q@kreacher>
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From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Because the PM-runtime status of the device is not updated in
__rpm_callback(), attempts to suspend the suppliers of the given
device triggered by rpm_put_suppliers() called by it may fail.

Fix this by making __rpm_callback() update the device's status to
RPM_SUSPENDED before calling rpm_put_suppliers() if the current
status of the device is RPM_SUSPENDING and the callback just invoked
by it has returned 0 (success).

While at it, modify the code in __rpm_callback() to always check
the device's PM-runtime status under its PM lock.

Link: https://lore.kernel.org/linux-pm/CAPDyKFqm06KDw_p8WXsM4dijDbho4bb6T4k50UqqvR1_COsp8g@mail.gmail.com/
Fixes: 21d5c57b3726 ("PM / runtime: Use device links")
Reported-by: elaine.zhang <zhangqing@rock-chips.com>
Diagnosed-by: Ulf Hansson <ulf.hansson@linaro.org> 
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---

v1 -> v2:
   * Initialize the "get" variable to avoid a false-positive warning from
     the compiler.

---
 drivers/base/power/runtime.c |   62 +++++++++++++++++++++++++------------------
 1 file changed, 37 insertions(+), 25 deletions(-)

Index: linux-pm/drivers/base/power/runtime.c
===================================================================
--- linux-pm.orig/drivers/base/power/runtime.c
+++ linux-pm/drivers/base/power/runtime.c
@@ -325,22 +325,22 @@ static void rpm_put_suppliers(struct dev
 static int __rpm_callback(int (*cb)(struct device *), struct device *dev)
 	__releases(&dev->power.lock) __acquires(&dev->power.lock)
 {
-	int retval, idx;
 	bool use_links = dev->power.links_count > 0;
+	bool get = false;
+	int retval, idx;
+	bool put;
 
 	if (dev->power.irq_safe) {
 		spin_unlock(&dev->power.lock);
+	} else if (!use_links) {
+		spin_unlock_irq(&dev->power.lock);
 	} else {
+		get = dev->power.runtime_status == RPM_RESUMING;
+
 		spin_unlock_irq(&dev->power.lock);
 
-		/*
-		 * Resume suppliers if necessary.
-		 *
-		 * The device's runtime PM status cannot change until this
-		 * routine returns, so it is safe to read the status outside of
-		 * the lock.
-		 */
-		if (use_links && dev->power.runtime_status == RPM_RESUMING) {
+		/* Resume suppliers if necessary. */
+		if (get) {
 			idx = device_links_read_lock();
 
 			retval = rpm_get_suppliers(dev);
@@ -355,24 +355,36 @@ static int __rpm_callback(int (*cb)(stru
 
 	if (dev->power.irq_safe) {
 		spin_lock(&dev->power.lock);
-	} else {
-		/*
-		 * If the device is suspending and the callback has returned
-		 * success, drop the usage counters of the suppliers that have
-		 * been reference counted on its resume.
-		 *
-		 * Do that if resume fails too.
-		 */
-		if (use_links
-		    && ((dev->power.runtime_status == RPM_SUSPENDING && !retval)
-		    || (dev->power.runtime_status == RPM_RESUMING && retval))) {
-			idx = device_links_read_lock();
+		return retval;
+	}
 
- fail:
-			rpm_put_suppliers(dev);
+	spin_lock_irq(&dev->power.lock);
 
-			device_links_read_unlock(idx);
-		}
+	if (!use_links)
+		return retval;
+
+	/*
+	 * If the device is suspending and the callback has returned success,
+	 * drop the usage counters of the suppliers that have been reference
+	 * counted on its resume.
+	 *
+	 * Do that if the resume fails too.
+	 */
+	put = dev->power.runtime_status == RPM_SUSPENDING && !retval;
+	if (put)
+		__update_runtime_status(dev, RPM_SUSPENDED);
+	else
+		put = get && retval;
+
+	if (put) {
+		spin_unlock_irq(&dev->power.lock);
+
+		idx = device_links_read_lock();
+
+fail:
+		rpm_put_suppliers(dev);
+
+		device_links_read_unlock(idx);
 
 		spin_lock_irq(&dev->power.lock);
 	}